The depth of maximum shower development and its fluctuations: cosmic ray mass composition at E_0 >= 10^17 eV

• Main Authors: Knurenko, S. P., Sabourov, A.
• Format: Text
• Language: unknown
• Published: arXiv 2010
• Subjects: High Energy Astrophysical Phenomena astro-ph.HE; FOS Physical sciences; Yakutsk
• Online Access: https://dx.doi.org/10.48550/arxiv.1010.1185; https://arxiv.org/abs/1010.1185

We present new data on Cherenkov light observations obtained during the period 1994-2009, after a modernization of the Yakutsk EAS array. A complex analysis of $\xmax$ and its fluctuations $σ(\xmax)$ was performed over a wide energy range. With the new data, according to QGSJet II model, an estimation was made of the cosmic ray mass composition for $\E \sim 10^{17} - 3 \times 10^{19}$ eV. The result points towards a mixed composition with a large portion of heavy nuclei at $\E \sim 10^{17}$ eV and the dominance of light nuclei at $\E \sim 10^{19}$ eV. The analysis of $σ(\xmax)$ energy dependence for the same energies qualitatively confirms this result. The shape of the $\xmax$ distribution at fixed energy $10^{18}$ eV is analysed to make more precise conclusions on cosmic ray mass composition. : Contributed paper to the XVI International Symposium on Very High Energy Cosmic Ray Interactions ISVHECRI 2010, Batavia, IL, USA (28 June - 2 July 2010). 4 pages, 5 figures